The present invention relates to the field of radiology instruments for acquiring images of a patient's body, which are principally usable in the medical field, in particular for cardiac or vascular examinations.
Radiology instruments with three axes of rotation are known, comprising an X-ray tube which is linked with a plane detector arranged opposite the tube and can occupy a plurality of positions in rotation in space around the body. These instruments are generally combined with a table, on which the patient rests and which can be moved in translation in the longitudinal direction of the patient's body, and in the height direction and in rotation about an axis transverse to the patient. The three axes of the radiology instrument are secant at a point which is referred to as the isocenter and on which the images which are obtained are centered.
For cardiac examinations, the region of the patient which is to be viewed is of small size in the length direction. For these examinations, a table with small-amplitude longitudinal travel is therefore used. Conversely, for vascular examinations, it is advantageous to be able to track the propagation of the contrast product which has been injected into the patient's vessels. It is therefore necessary to move the patient from his head to his feet so that each part of the patient passes successively through the isocenter of the radiology instrument. The consequence of this is that a table with large-amplitude longitudinal travel is necessary.
The X-ray tube and the image detector of the radiology instrument are arranged on either side of the patient, one of these elements being in general above the patient and the other below the table, and the table transparent to the X-rays. The space under the table therefore needs to be clear in line with the isocenter in order to not only position one of these elements, but also to move it with different angulations. A table provided with an off-center leg away from the isocenter should therefore be used, with the surface of the table overhanging relative to this leg. Such a table with large-amplitude longitudinal travel is bulky and heavy and undergoes high mechanical stresses. The table surface tends to flex when in the maximum extension position and is supporting a heavy patient, which may compromise the accuracy of the examinations carried out and the patient's comfort. The fact that it overhangs relative to the leg of the table may also be a source of psychological discomfort and stress for the patient. Furthermore, for equivalent technology, a large travel entails a greater motive force, which is a problem for the doctor.
A table is known whose leg is provided with a cam allowing two working positions, which is marketed by the company PHILIPS. The overhang is reduced by this arrangement. Nevertheless, this table may have a tendency to vibrate in response to the external environment, which impairs the accuracy of the examinations. The area which the table passes through when it is being moved from one position to another tends to increase in size and may cause a problem of safety for the staff in charge of handling it, as well as a problem with the cleanliness of the room in which it is located.
A radiology instrument with three axes is also known which is marketed by the company SIEMENS and in which the base is mounted on a cam allowing two longitudinally offset working positions. This instrument has similar drawbacks to the one mentioned above.